Thoughts on cycling and cycling performance

April 25, 2011

Bicycle Aerodynamics

Improve Cycling Performance with Optimal Bicycle Aerodynamics

If you are an aspiring time trial specialist or triathlete, then you should be very concerned about optimizing bicycle aerodynamics in order to improve cycling performance.

The bottom line is that there are only three ways to go faster on a bike – generate more power, reduce aerodynamic drag or mitigate rolling resistance. A successful cyclist must work on all three elements.

Athletes tend to put a lot of time and effort into improving fitness (i.e., pushing more watts). But let’s face it, unless you are a young, emerging professional athlete, you can only become so fit as a cyclist or triathlete. Yes, taking full advantage of your God-given V02 max through focused endurance training is important. Likewise, improving your functional threshold power is also a vital aspect of improving cycling performance. But, if you are an age group cyclist or triathlete, you only have so much time to train, recover, adapt and improve. Even then, your improvement in cycling performance will be limited by your physiology.

So, why not work on “free speed” as my favorite cycling coach calls it? That is, get faster by reducing aerodynamic drag.

(And, oh, by the way, it’s not all free).

What Is Aerodynamic Drag?

As the bicycle and rider move along the road, air exerts a force that increases sharply with speed. As this graph shows, it may only take 200 watts to roll along at 35km (21.37mph), but it takes almost 300 watts – a 50% increase in power – to travel at 40km (24.84mph) for a mere a 16% increase in speed. So, the ratio of power output to speed rises dramatically as speed increases. For example, it takes approximately 15 extra watts to go from 20 to 21 mph. However, it takes an additional 37 watts to go from 30 to 31 mph, more than double the effort for the same increase in speed. Thus, a rider who is able to push 300 watts at threshold reaches terminal velocity – the point at which forward force (bike speed) and opposing force (air resistance) equalize – at approximately 40km/hour. The only way to go faster is push more watts (a physiological challenge) or reduce aerodynamic drag (a physics challenge with high potential reward).